Disc drives include one or more heads including read/write transducers. Each head is mounted in an air bearing slider. During operation, a disc rotates at a high speed, which generates an air current immediately adjacent to the surface of the disc. The air currents act upon a lower air bearing surface of the slider and generate a lift force to direct the slider away from the disc and against a load beam. This causes the slider to fly at an ultra-low height above the disc. For the disc drive to function properly, the slider must maintain the proper fly height and provide adequate contact stiffness to assure that the slider does not contact the disc during operation.
Decreasing fly height of the slider allows transducers in the head to achieve greater resolution between the individual data bit locations on a disc. It is desirable to have heads fly as close to a disc as possible. Furthermore, fly height precision is directly related to drive reliability in all disc drives, and, in general, greater fly height precision is required as data storage density of a disc medium increases.
In a conventional air bearing slider, the slider body is formed from a substrate wafer of conductive ceramic material. On this substrate, a thin film of insulating material is deposited, and a metallic transducer is built therein, by a process such as sputtering. The transducer, which typically includes a writer portion for storing magnetically-encoded information on a magnetic media and a reader portion for retrieving that magnetically-encoded information from the magnetic media, is formed of multiple layers successively stacked upon the substrate. The volume of the transducer is typically much smaller than the volume of the substrate.
Heads are often designed to include a pole tip recession (PTR), which is the distance the pole-tip of a transducer is recessed from the bottom surface of the slider. The spacing between the transducer and the disc is equal to the PTR in addition to the fly height. Manufacturing variances in transducer heads, sliders, gimbals and load beam assemblies result in different fly heights and PTRs, which limits precision in spacing between a transducer and a disc.
Accordingly, some transducer heads include a deformable material that allows the transducer-disc spacing to be adjusted to account for variances in fly height and PTR in an assembled disc drive. A deformable material may be integrated within the head during manufacture by adding an additional layer on the substrate. For example, a transducer head may include a material with known thermal expansion properties and a heater that can be set to a plurality of settings. Each setting corresponds to a PTR adjustment according to the thermal expansion properties. After assembling a disc drive, as part of the manufacturing process, heater settings are incrementally increased until the transducer head contacts the media surface. At this point the PTR could be said to be a pole tip protrusion since the pole tip actually extends beyond the bottom surface of the slider. Using the known heater setting at which the transducer head contacts the media surface and known heater response function, an operational heater setting corresponding to an optimal PTR adjustment is calculated. The operational heater setting is less than the heater setting at which the media surface is contacted, such that the transducer is retracted from the media surface. During operation of the disc drive the heater operates at the calculated heater setting. In this manner, the PTR for each head is adjusted as part of the manufacturing process to increase precision in the distance between a transducer and the rotating disc medium beyond the physical capability of the utilized manufacturing processes.